They will both give you excellent pre-emergent control of various annual grassy and broadleaf weeds. Dithiopyr provides some post-emergent crabgrass control, but that's typically not an issue unless you're very late with your app. Given the price difference prodiamine is a no-brainer.

Thanks lawniac. I appreciate your comment and will be making the switch to Prodiamine. Another issue that I have had with Dimension is that I could not find out what the ratio of water to product should be for small pump sprayer applications. I was told that there was no ratio and the volume of water did not matter as long as you ran out of product after spraying an acre. But my somewhat and sometimes logical mind tells me that if I use (max) 2 pints (32 ounces) for one acre, then a 500 sq. ft. area would require approximately .37 of an ounce and adding 2 gallon of water to a portable tank sprayer might might work out. Hope I'm not too far off the rails with this. Anyway, with Prodiamine, it appears that the ratio per gallon is defined.

That is correct, the amount of carrier you dissolve the product in does not matter, except in that you want to have enough carrier to cover the entire area. What matters is the amount of product per 1000 sq ft. So if your application rate is 0.75 oz per thousand, you can dissolve that in one gallon of water and apply the whole gallon over 1000 sq ft or you can dissolve it in 5 gallons of water and apply the whole 5 gallons over 1000 sq ft. In both situations you got 0.75 oz of product per thousand.

So the ratio of product to carrier doesn't matter. They do give a minimum amount as a general guide of what they feel would be needed to get decent coverage, but it's up to you and your equipment. I'll give you an example - it takes me 4 gallons of water walking at about 4 mph with a sprayer that puts out 0.8 gpm to cover a 2,000 sq foot area. If you came over and walked at the same pace with a sprayer that only puts out 0.4 gpm, you would cover the entire area with only 2 gallons of water. You can imagine, if you change walking speed that impacts it too, so if you walked at half the speed you'd also end up using 4 gallons. So, I would dissolve my 1.5oz of prodiamine in 4 gallons of water, you would dissolve it in 2 gallons of water, and we would both end up applying the same amount of product but in different amounts of water due to the sprayer difference.

The easiest way to do it - this is called "calibration" - is to spray the area at a comfortable pace with plain water. See how much water it took. This is the amount of water you will want to dissolve your prodiamine in.

Thanks again lawniac. Now I'm starting to think more like a farmer. Very interesting and I assume the farmer's appreciate their needed GPS equipment in today's world. I use my iPhone with a speed checker to determine how fast to drive mequipment in the yard; golf cart or zero turn. But your explanation is bringing home the tools to help determine how much product to use in a walk-along sprayer. My guess is that some homeowners struggle with this stuff as well. Anyway, I appreciate your taking the time to communicate and I'll bet it helps a few other folks as well. The short of this story must be "the older you get, the more water you need." :-)